1. Field of the Invention
Castable and curable polyurethane-urea polymers having improved flow and end-waste characteristics suitable for providing an insulating thermal barrier in a metal, especially in an aluminum, extrusion.
2. Background of the Invention and Prior Art
There are many types of castable thermosetting polyurethane and polyurethane/urea elastomers of various compositions available on the market today. Many of these materials contain polyamines. However, when used as a structural thermal barrier in metal, e.g., aluminum, extrusions, the polyurethanes and/or polyurethane ureas and/or other polymers currently on the market have serious limitations. For example, the standard polyurethanes necessitate the application of tape to the ends of the extrusion to contain the liquid polymeric component until it gels and hardens or cures. The reason for taping is based on the pour and debridge system in widespread use. The isocyanate and resin components are metered volumetrically by a pumping system. The pumping system moves the component materials from tank reservoirs to a mixing head which blends the chemicals using either a static tube or a mechanical mixer. The blended chemicals then flow through a dispensing tube into an open-ended U-shaped cavity provided in the extrusion. Up to the present invention, the open ends of such cavities have required taping so that the liquid polymeric chemical did not flow out before hardening. Once the chemical has hardened properly, the extrusion is transferred to a debridge saw where the bottom side of the U-shaped cavity is removed, leaving a non-conductive "thermal barrier" of polymeric material between the two sides of the extrusion, as shown in the drawings.
The material of the present invention is a castable and curable thermosetting polyurethane/urea polymer which has improved gelation characteristics, especially as they relate to the insulating thermal barrier metal, especially aluminum, extrusion industry. These gelation characteristics are unique and provide a condensed or diminished flow time when compared to standard polyurethane systems. Flow time can be described as the time from which the mixed liquid polymeric components flow freely until the time at which the partially reacted but still reacting materials no longer flow. The flow time of the materials of the present invention has been reduced to not greater than about six seconds, preferably not greater than about two seconds, while essentially maintaining normal gel times. This decreased flow time characteristic provides an important advantage, namely, the elimination of the necessity of taping the ends of extrusions during the filling operation, which was previously necessary, and at the same time substantially decreases the end waste of the extrusion. The end waste is the leading and trailing portion of an extrusion which contains insufficient polymeric, e.g., polyurethane, filling, due to polymeric material running out of the extrusion, or due to shrinkage of the polymeric material during its transformation from a liquid to a solid.
As stated, the material of the present invention thus provides several advantages. Up till now, there has been a need to have some means by which adhesive tape was applied to the ends of the extrusion channel involving either a manual or mechanical method. The present material gives an immediate increase in viscosity and eliminates the need for taping the extrusion ends and thereby decreases labor and cost. The non-flowing characteristic of the present material, produced from commercially-available ingredients to achieve the end result of a pour-in-place thermal barrier, is unique to the industry. This material does not require thixotropic agents, fillers, or fibers to achieve the end result, is produced using typical mixing and metering equipment already found in the industry, and can be used in place of the now standard materials of the industry to eliminate the need for extrusion taping.
The non-flow behavior of the material of the present invention has the added advantage that poured liquid polymer does not slosh in the extrusion cavity, even without the addition of fillers, fibers, or thixotropic additives to achieve this end. It appears to be less sensitive to atmospheric moisture than typical polyurethane systems, as well as less sensitive to temperature extremes which affect the curing characteristics of polyurethanes. It has little to no "nozzle buildup" coupled with low linear wet shrinkage, whereas typical systems in the industry have either some nozzle buildup with little linear wet shrinkage or little nozzle buildup with higher linear wet shrinkage, nozzle buildup being the coating of the interior of the nozzle with reacted polymer and linear wet shrinkage being the shrinkage usually obtained at the ends of the extrusion when the material is transformed from a liquid to a solid. Also, coupled with the non-flowing nature of this material is the advantage of less cleanup time of involved machinery since, in usual practice, there is typically some spilling and flow from the ends of the extrusion, especially if the tape does not adhere well to the metal, but such a problem is minimized or eliminated with material of the invention.
Most molded plastics, molded in usual open or injection molds, or extruded into cavities by "cavity extrusion", for example, into a cavity in a window frame, suffer from the foregoing disadvantages, but the polymeric product of the invention does not. The thermally-stable short-flow time polyurethane-urea polymer of the present invention is constructed from a carefully selected combination of commercially-available reagents, and the invention comprises the utilization of these components, which are of course old in themselves, in such a manner as to produce the final end product, the castable and curable thermosetting polyurethane-urea polymer, which is ideal for pouring in place as a thermal barrier, which serves a purpose which is not attainable by or with previously-available products, and which, by its very definition, is unique in the field. In particular, the polyurethane-urea polymer of the invention, when employed as a structural component, most conveniently can serve as an insulating medium in a thermalized (thermal barrier) aluminum extrusion window or door frame. Thus, the present invention provides a castable polyurethane-urea polymer which may be employed in a wide range of molded products. It can be painted and may be used for decorative purposes and for end products which are cast molded. It is also unique because its properties can be achieved without the addition of fillers and fibers and because it may conveniently be dispensed through conventional low-cost, low-pressure, plural component metering mixing machines.
The product of the invention has a well established market in the thermalized or thermal barrier aluminum extrusion window and door frame market, and in like applications. Using the conventional and generally-available equipment, but substituting the unique castable and curable thermosetting polyurethane-urea polymer of the present invention, which is characterized by improved flow characteristics, the art can readily adapt to the employment of the advantageous polymer of the present invention and utilize all of the desirable characteristics thereof to considerable operating and economic advantage.
Although the polymeric product of my U.S. Pat. No. 5,130,404, entitled Castable Thermosetting Polyurethane Polymer Having Improved Heat Stability, issued Jul. 14, 1992, is a definite step forward in the art, being characterized by excellent heat stability, it does not solve the problems of flow time and end waste without end taping, which are addressed and solved by the present invention.